This invention relates in general to a novel lubricant for intravenous (IV) catheters. IV catheters are generally used on patients to infuse liquids, such as normal saline, glucose solutions and drugs, into the patient. These catheters are also used to withdraw blood from the patient for blood gas and other analysis.
In order to place a catheter in a patient's vein, a sharp introducer needle must be used to puncture the skin, tissue and vein wall to provide a path for placement of the catheter in the vein. Typical IV catheters are "over-the-needle" catheters where the catheter is coaxially placed over the needle. The distal tip of the catheter is located adjacent to and proximal of the sharp distal tip of the needle. Preferably the tip of the catheter adheres slightly to the tip of the needle to ensure that both the catheter and needle travel together through the skin, tissue and vein wall and into the patient's vein. The adherence is achieved by making the inner diameter of the catheter tip slightly smaller than the outer diameter of the needle.
Placement of the catheter and introducer needle into the patient causes sharp pain to the patient. In order to facilitate insertion of the catheter and introducer needle into the vein and to minimize patient discomfort, the catheter and needle can both be lubricated. Most IV catheters are lubricated with polydimethylsiloxane silicone fluid. However, some IV catheters are not lubricated at all.
The polydimethylsiloxane silicone fluid may be applied to the surface of the catheter and needle by wiping the surfaces with the lubricant. Alternatively, the catheter and needle can be separately dipped into a solution of polydimethylsiloxane silicone fluid and a solvent. This is generally the preferred method of applying the lubricant because a consistent, controlled and uniform coating can be achieved. The polydimethylsiloxane silicone fluid must be dissolved in an organic solvent because the silicone oil in this compound is hydrophobic. Typically, the solution contains 2.5% silicone oil. The catheter and needle are then separately dipped into this solution.
Until recently the preferred solvent has been freon because it is non-flammable and flashes off, i.e. evaporates, readily after the polydimethylsiloxane silicone fluid solution has been applied to the catheter and needle. Although freon has been preferred, it does suffer some drawbacks. For instance, the high evaporation rate of freon causes the polydimethylsiloxane silicone fluid to concentrate on the surface of the solution in which the catheter and needle are dipped. Because of this high evaporation rate, the solution is difficult to control. Moreover this solution is expensive because of the large loss of freon during the coating process. In addition, freon is a chlorofluorocarbon (CFC) which is thought to react with and destroy the earth's protective ozone layer. Thus the manufacture and use of such CFC's will eventually cease in the near future.
Other solvents will have to be used in order for silicone fluid to be applied to catheters and introducer needles as a lubricant. Other solvents include alcohol and hydrocarbons. However, alcohol and hydrocarbons are highly combustible and are therefore too dangerous for use in manufacturing.